directory structure change to work with glide

glide has its own requirements. My previous workaround caused me some
code checkin errors. Need to fix this.

weed/storage/crc.go

@@ -0,0 +1,30 @@
+package storage
+
+import (
+	"fmt"
+	"github.com/klauspost/crc32"
+
+	"github.com/chrislusf/seaweedfs/weed/util"
+)
+
+var table = crc32.MakeTable(crc32.Castagnoli)
+
+type CRC uint32
+
+func NewCRC(b []byte) CRC {
+	return CRC(0).Update(b)
+}
+
+func (c CRC) Update(b []byte) CRC {
+	return CRC(crc32.Update(uint32(c), table, b))
+}
+
+func (c CRC) Value() uint32 {
+	return uint32(c>>15|c<<17) + 0xa282ead8
+}
+
+func (n *Needle) Etag() string {
+	bits := make([]byte, 4)
+	util.Uint32toBytes(bits, uint32(n.Checksum))
+	return fmt.Sprintf("\"%x\"", bits)
+}